HF radio

[Jan Olieslagers]

I have some questions about HF (short-wave) radio equipment:

-) where is this mandatory? I understand it is required for G/A planes crossing the North Atlantic. Also ISTR it was being fitted on the ex-Sabena planes that were going to be operated in African ventures, first AirDC, now Korongo.
-) what are the specs for such equipment? frequency range, channel separation, bandwidth, transmitter power?
-) what kind/type of antenna would/could be used?
-) are any available from the major avionics suppliers?

NB not sure if this is the right place for this kind of question, admins pls feel free to relocate.

[Di_Vosh]

G'day Jan,

I can give you answers for Australia:

1: In Australia it is mandatory for IFR flights to be in continuous radio communications with ATC. In many parts of Oz it isn't possible to get VHF comms on the ground, so HF must be used.

2: Typical frequencies used here are anywhere from 3452 to 17907. In most areas we have the choice of around 3 or 4 frequencies; most are separated by at least 1500 Hz

3: Cable antenna (all I've ever seen). A typical setup is from the top of the cabin to the leading edge of the fin, then to a wing-tip. Another setup is a length under the fuselage.

4: I would imagine so.

Hope this helps

DIVOSH!

[Exaviator]

Cable antenna (all I've ever seen). A typical setup is from the top of the cabin to the leading edge of the fin, then to a wing-tip. Another setup is a length under the fuselage.

Back in time we also had a trailing antenna which was wound out prior to use, and wound back when no longer required. The latter action often overlooked, and the antenna usually ended up draped over the airport fence after landing. :hmm:

[piggybank]

Exaviator, yes I remember that with the Beaver in the early 70's, it was certainly a long antenna that was uncoiled for that. Was it for the Sunair radio fit?

Where we have the HF antenna on a helicopter, I am thinking of 212s and Pumas I have worked on, the antenna used to be a long 'wire' zig zagging to the tail rotor area on standoff posts, and ideally in a strong nylon mesh hose in case the antenna broke.

Indonesia and Papua New Guinea still require HF to be fitted to the aircraft.

[HEATHROW DIRECTOR]

The HF antenna on large aircraft is usually inside the vertical rudder fin, behind a composite (non-metal) fairing. On the Boeing 707, however, the HF antenna is a horizontal mast that points forward from the top of the rudder fin. The precise configuration varies between aircraft types and, probably, new innovations appear on modern aircraft.

[Liobian]

If you are planning to cross the N Atlantic, carriage of serviceable HF is mandatory in Shanwick OAC airspace. IIRC you are permitted to route via Iceland, without HF - that would include transit at N61W010. For full info, see UK AIP. :ok:

[eckhard]

I believe HF is also required in the Gander OCA below FL250.

[galaxy flyer]

Eckhard

True, but there is a dead spot over the Davis Strait. Last time I had both HFs inop, all was well until Island turned us over to CZQX south of Prinz Christian, the GanderRadio operator seemed to expect to lose comm with us until 50W.

GF

[eckhard]

GF

Absolutely. Although HF is required below FL250, it doesn't guarantee VHF coverage above FL250!

I regularly fly FL280-FL340 between Goose and Narsarsuaq without HF and am out of ATC comms for a while between LOACH and 50W. Relaying on 123.45/121.5 works most of the time!

Eck

[toby320]

does somebody knows about if HF is mandatory to cross south atlantic I mean from cabo verde (africa) to brasil or some caribbean island???

[eckhard]

The shortest direct distance across the S.Atlantic is from Fernando de Noronha (an Island off Brazil) to Freetown, Sierra Leone. This measures 1372nm. As VHF coverage is generally limited to 200nm, that would leave a 972nm 'VHF gap' in the middle.

From Sal, Cape Verde to Noronha it is slightly shorter: 1353nm.

Even if you route vis Ascension and Robertsfield, the distances are 1105nm and 882nm, so I think you can assume that HF is required for this route.

[411A]

....so I think you can assume that HF is required for this route.

Oh, its required, alright.
Just don't presume that some stations might answer your urgent calls.:rolleyes:

[Dan Winterland]

And some stations just want to talk to you so they can charge you the 'navigation' fee.

The device in the fin of some big aircraft isn't the HF aerial, it's the ATU - the Aerial Tuning Unit. The whole airframe is used as the aerial and the ATU balances the load and matches it to the frequency. This is why you should never transmit on HF while refuelling.

[V1... Ooops]

... I understand it is required for G/A planes crossing the North Atlantic...

The Canadian procedures for crossing the North Atlantic provide one route that may be used by aircraft that are not equipped with an HF radio. The details are probably the same as what Liobian referred to in his earlier post.